A conventional laser gyroscope includes a coil of optical fibre waveguide wound around a circular former. Laser light is injected to travel in opposite directions around the coil and then, the light beams emerging from both ends of the coil are synthesised and applied to a light detector. By analysing the output of the light detector information on changes in phase and hence the rotation of the coil in space can be obtained.
Attempts have been made to manufacture an integrated optics ring resonator for a laser gyroscope by using a planar substrate and then forming a flat ring of higher refractive index in that planar substrate. Such integrated optics ring resonators rely on total internal reflection to contain light in both the plane of the planar waveguide and in the radial direction. Total internal reflection tends to cause losses especially in the radial direction at the lateral edges of the planar waveguide as a result of the roughness of this interface.